104 GOBIOIDS. 



tulous ; there is a band of villiform teeth on each intermaxillary and 

 premandibular bone. 



The Helost07nes{\) are remarkable for the small size and shape of 

 their mouth, which resembles the head of a nail driven into the 

 muzzle, whence their generic name ; their teeth are not less extraor- 

 dinary, being attached solely to the inside of the lips, and moving 

 with them ; they may be regarded, in fact, as a row of slightly calci- 

 fied labial ciliiform papillse. The palatines and vomer are edentulous ; 

 the posterior and inferior pharyngeals support small conical teeth. 

 In the genera Colisa, Macropodus and Trichopus, the teeth are 

 attached to the jaws, but are very small or villiform ; the anterior 

 maxillary teeth in the Gourami {Osphromenus), are a little longer 

 than the rest. The Spirohranchus is the only genus among those with 

 labryrinthiform pharyngeals which has palatal teeth. These are 

 short, coarse and villiform ; there are similar teeth on the vomer, 

 intermaxillary and premandibular bones ; the side teeth in the latter 

 locality are longer than the rest. 



44. The fishes of the family called Theuties, by Cuvier, have a 

 small mouth, with a single row of teeth on the intermaxillary and pre- 

 mandibular bones ; the palate and vomer are edentulous. 



The jaw-teeth of the Axinurus are extremely slender ; those of the 

 Naseus are simply conical and sharp-pointed. 



In the genera Prionurus, Priodon, Amphacanthus and Acanthurus, 

 the teeth are commonly notched or serrate at the margins. Mr. Andre 

 has given an accurate magnified view of the external form of the teeth of 

 the Acanthurus nigricans, {Chcetodon nigricans of Linnaeus), in the Phi- 

 losophical Transactions, and had recognized the arborescent medullary 

 canals in the body of the tooth, " through which," he says, " the 

 blood-vessels ramify, which are destined for its growth and nourish- 

 ment." He very justly observes, that a fish having teeth of a crys- 

 talline hardness, and arranged in a single row, cannot be naturally 

 associated with the Chsetodonts, which are characterized by nume- 

 rous rows of flexible teeth, of a totally diflerent form. 



The medullary canals in the maxillary teeth of the Acanthurus 

 nigricans are directly continued from a conical pulp-cavity at the 



(1) 'Ao^, a nail; ^"jwa, a mouth. 



